This proposal describes the development and optimization of novel reagents and technologies to measure and experimentally perturb growth and activity-dependent plasticity of neuronal dendrites in Drosophila central nervous system neurons in vivo and examine their outcome on long-term behavioral adaptation. These techniques effectively combine behavioral analysis on one hand with transgenic labeling of individual central nervous system neurons with visible fluorescent markers (e.g. GFP), concomitant expression of proteins of choice in these neurons, confocal microscopic imaging of neuronal dendrites, and 3D reconstruction of these dendrites using dedicated computer algorithms on the other. We use this suite of techniques to test the hypothesis that the Myb-related transcription factor Adf-1 regulates learning and memory in Drosophila by controlling structural and functional properties of neuronal dendrites, downstream of a signaling pathway driven by CaMKII, as proof of principle. Adf-1 is expressed widely in the fly nervous system including motor neurons and higher brain regions required for learning and memory, similar to reported Myb expression in the vertebrate brain. Strikingly, mutants in Adf-1 (called nalyot) are also reported to have dramatic deficits in long-term memory formation. Results obtained thus far suggest Adf-1 strongly regulates dendrite growth. Based on these observations, we propose that neuronal Adf-1, by regulating activity- dependent plasticity of neuronal dendrites, instructs cellular mechanisms that control long-term behavioral adaptation (including learning and memory). Upon conclusion, these studies should not only reveal fundamental molecular mechanisms that, through regulation of activity-dependent dendritic plasticity, control learning and memory, but also firmly establish widely useful techniques to measure structural and functional plasticity of dendrites in the context of long-term behavioral adaptation.